Washington D.C. (including Baltimore) - Prices at IAD duty free?

Has anyone passed through there recently? I want to take a friend in the UK a bottle of single malt. I'm traveling United (who don't seem to sell a single malt on board :() so my choices are use the duty free or buy it at my local liquor store. For "average" booze, the liquor store is cheaper, but I'm not sure about higher price points.

TIA